Rh factor, family history and risk of breast cancer: A case-control study in Uruguay

Objective: To explore possible relationships among blood factors, family history of breast cancer (BC) and the risk of the disease, a case-control study was carried out in Montevideo, Uruguay. Methods: Eight hundred and one patients were interviewed, including 252 certified cases of BC and 549 frequency-matched controls. Blood groups (ABO, Rh) were obtained from medical records. Multivariate analyses were performed, adjusting for age, selected menstrual and reproductive factors, and family history of BC as well as of other cancers. Results: We found that the absence of Rh factor (Rh−) was positively associated with the risk of BC (adjusted Odds Ratio [OR] = 1.49, 95% Confidence Interval [95% CI] 1.05-2.11). Stratified analyses by family history of BC showed a strong association for Rh− with a positive history of first degree relatives (OR = 3.17, 95% CI 1.06-9.47). Also stratified analyses by family history of other cancers showed a positive association for Rh− with a positive history of first degree relatives (OR = 2.08, 95% CI 1.05-4.11). Conclusion: Regarding the implications of an inherited factor like Rh and its associations with the family history of BC, it might increase the probability to generate high-risk individuals if further studies confirm the present preliminary findings.